Firearm



Aug. 21, 1945. M. H. WALKER FIREARMS Filed April 5, 1944 2 Sheets-Sheet l INVENTOR.

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Aug. 21, 1945. M. H. WA/LKER FIREARMS Filed April 5, 1944 '2 Sheets-Sheet 2 INVENTOR. MERLE fl. hMZ/(Efi? I. ll

Patented Aug, 21a 1 945 ton Arms Company, Inc., corporation of Delaware a'em t o n a Ap plication A pril 5,1944, Serial No. 529,640 ZCIaims. (on. 29-11) This invention relates to the rifling of: the

- barrels of firearms, particularly barrels of small caliber, and contemplates certain improvements and refinements in previous rifiing practices especially intended to facilitate mass production. The bores of the steel or alloy barrels of all Fig. 21s a section of the riflingtoolof 1.

modern firearms intended to dischargea single I, projectile on each firing comprise spiral grooves which "are engaged by the softer metal of the projectile and impart to the projectile the rotary motion necessary for accurate sustained flight. The'nur'nber of such grooves varies betweenwide limits. In ordinary practice, the barrel blank in the form of a bar or forging is drilled and reamed to form a bore of substantially the desired-land diameter, the lands being the areas separating the grooves; Metal is then planed from the areas between the lands by passing through the bore a planing or rifling tool. For barrels of relatively large bore (not less than .3")- it has been found feasible to use multiple bit tools (broaches) by which the rifiing can be com-. pleted in a small number of passes, or even in a single pass, of the tool. However, in the conflnement of the smaller bores of shoulder rifles broaching presents dimcult problems of tool support, chip removal and lubrication.

The widely used single bit rifling tool is usually arated by grooves 18.

Fig. 3 is an elevation of a rifling tool blaank. 'Fig. 4 is a section of'a die used in the making Fig. 5 is a diagrammaticrepresentation of a rifling machine adapted to the practice and processes ofthe invention. The rifiing tool illustrated'in Fig. 1 comprises a somewhat elongated pilot l0, a tapered lead section H, and a shortcylindrioal head I2 having thereon the, inclined rifling ribs- I 3, the surfaces of which merge with the lead surface t l. it has been found that milled tools, if operable at all, are of comparatively short life, and the present invention contemplates the forming of the rifling ribs H by swaging. This is accomplished by the application of a swaging die, a typical form of which is illustrated. .in Fig. 4, to a blank of the form shown in Fig. 3. The di assembly includes a die holder i5 and the die proper IS, the die aperture comprising spiral lands 11 sep- Toprepare the die assembly, a barrel made of tool steel is rifled in the conventional manner, and a section of the desired length cut therefrom and hardened to' form die I 6, which is then press fitted into holder the full width of the desired groove, and re-' moves .0002" of metal at eachpass. Since the groove depth is about .004", about twenty (20) passes per groove are required, and the complete rifiing of a barrel becomes a lengthy oper ation, and complex machines are required Tor spiraling the tool through the bore, returning the tool, and indexing the barrel between passes of the tool. Y

Some efforts have been made to rifle barrels by means of swaging. A tool which has been milled with spiral ribs corresponding to the rifling grooves is forced through the length of the barrel, forming therein by metal displacement spiral grooves which are the counterpart of the raised ribs on the tool, Prior to the present invention, the swaging of rifling in barrels less than .50 caliber has not been, successful, on account of the excessive friction between the use.

l5. The die assemblies of Fig. 4 are made of a size convenient for machining and handling. The tool blank of Fig. 3, comprising pilot I00, taper H0 and. elongated head I20, is turned from softened tool steel and is plated with a suitable friction reducing metal, such as copper, tin, lead,

cadmium or 'zinc. The plated tool, being adequately lubricated with'a semi-solid lubricant, is then forced into the'die of Fig. 4a distance suflicient to form a rifling head l2 of the desired length. For a .30 caliber barrel, a preferred length is about The tool is then withdrawn from the die, the excess length of head I20 is removed and, after hardening, the tool is ready for Barrels to be rifled in accordance with the L present lnvention'may be processed through the preferably about .001" under that of barrels to rifling tool and the bore surface and the excessive strains imposed on both the work and the tools. The present invention contemplates certain new discoveries and refinements of process which have enabled the quantity rifling of the barrels of all shoulder rifles, including .22 caliber. In the drawings: r Fig. 1 is an elevation of a rifling tool.

be rifled in the customary manner. The barrels of some rifles are tapered, the cross-sectional area adjacent the muzzle being substantially less than that adjacent the breech. Such barrels may be rifled by the process of this invention, after outside turning, with a resulting bore diameter within accepted manufacturing tolerances.

However, if greater accuracy is desired, the riding 'ment at sections of reduced wall thickness.

should be performed before outside turning, so that during rifiing the barrel is of substantially the same thickness from end to end. Swage rifling applies substantial stress to the barrel metal, with a tendency for greater bore enlargey swage rifiing'and stress relief annealing before outside turning, very high accuracy taperedbar- 39 mounted for sliding movement on the machine rels can be secured; and if the finished barrel is way. The guide plate 3! adjacent the head stock is held for limited movement relative to the head stock by a headed bolt "I which passes freely through an aperture in plate IO, and is threaded into a lug "I secured to or integral with the head stock It. The remaining guide plates are arrangedfor limited movement relative to each other, the construction being suchthat as the push rod 34 is advanced into the barrel the suide 'plates, which were originally appropriately tapered bar'relswhich are swage rifled accord ing to the present invention after outside turning, is within accepted tolerances.

In preparation for swage 'rifiing according this invention, the bores of the drilled and reamed barrels, having been degreased and washed, are given a thin plating of copper,1tin, lead, zinc, cadmium. or other anti-friction metal; Copper has been found to be particularly useful for this purpose, being applied by passing through the bore tobe plated a suitable solution of copper sulphate or of one.of the proprietary plating salt mixtures, such as cuprodine." For this purpose, the barrels are preferably arranged in a vertical position and the plating solution introduced at the upper ends along with sufficient air to preclude the formation of air pockets which might interfere with uniform distribution of the solution. A solution of -cuprodine" prepared in ac-- cordance with the manufacturer's directions will satisfactorily plate bores in about one-and-onehalf minutes.

An appropriate quantity of a suitable semisolid lubricant is then introduced into one end of the bore; the rifling tool of Fig. 1 is inserted in the lubricant, pilot end first, and is then pushed through the bore. The pushing of a rifling tool through the bore can be accomplished in a very simple machine, as distinguished from the complex rifiing machine. The tool is its own guide, the spiral rib thereon forming a counterpart spiral groove in the bore without forced rotation of either barrel or tool. The essentials of the machine are merely barrel holding means and adequately supported and guided tool pushing means. I

Fig. 5 illustrates diagrammatically one form of such machine. One end of the barrel 25, preferably the muzzle end is received in a suitably tapered aperture in a stationary supporting block 26. Near its opposite end the barrel is clamped between suitable jaws 21 and 28 held in tapered ways in a fixed supporting block 29 and propelled into clamping position by their engagement with short arms 30 and 3| projecting from an arbor 32 provided with a manipulating handle 33. The rifling tool is shown in place in the end of the barrel. In alignment with the barrel is a rifiing tool push rod 34, one end of which is received in a bushing 35 suitably held in a head stock 38 provided with a boss 31 which receives a feed screw 38 by which the head stock is moved along a fixed guideway. To prevent buckling of the long slender push rod 34, said rod is passed through apertures in a plurality of guide plates spaced throughout the length of the push rod, move together adjacent the end of the barrel. For this purpose, each guide plate is provided withapertures which loosely receive the ends of connecting bolts 40. Each bolt 4| passesfreely through two adjacent guide plates and is retained therein by suitable end fastening means, such as nuts 4|. Each guide plate 3! comprises a suflicient number of apertures so located as to freely pass thenuts 4| when the guide plates are moved together. To the supporting base 42 of the guide plate adjacent the barrel there is secured a short cable 43 passing over a pulley 44 and supporting a weight 45 adequate to move each of the guide plates of the assembly into the position determined by bolts 4|! and nuts 4|. Correct positioning of the guide plates when the push rod is retracted is thus insured.

It will be understood that the machine as described is only a representative means for practicing one part of the invention.

What is claimed is:

1. In the manufacture of rifled gun barrels, the method comprising the steps of forming a hole through the length of a barrel blank, said blank having a substantially uniform exterior diameter from end to end, plating said hole with an anti-friction metal, inserting into said hole a swaged forming tool of substantially the diameter of said hole and having raised spiral surfaces, pushing said tool through said plated barrel to form grooves in the walls of said barrel hole by plastic deformation of the barrel metal, relief annealing said blank after said plastic deformation to relieve expansion stresses set up by said plastic deformation, and subsequently exteriorly tapering said blank to the desired finished barrel configuration.

2. In the manufacture of rifled gun barrels, the method comprising the steps of forming a hole through the length of a barrel blank, said blank having a substantially uniform exterior diameter from end to end, plating said hole with copper, inserting into said hole a swaged forming tool of substantially the diameter of said hole and having raised spiral surfaces, pushing said tool through said plated barrel to form grooves in the walls of said barrel hole by plastic deformation of the barrel metal, relief annealing said blank after said plastic deformation to relieve expansion stresses set up by said plastic deformation, and subsequently exteriorly tapering said blank to the desired finished barrel configuration.

MERLE H. WALKER. 

